CONSUMPTION OF FUEL.

Press, Volume LXVIII, Issue 20587, 1 July 1932, Page 8

CONSUMPTION OF FUEL.

EFFECTING A REDUCTION. HOW TO MAKE ECONOMIES. In . considering the matter of fuel consumption, many motorists are inclined to think that the size of the carburettor jet is the only important factor. Tlie reason for this opinion, or course, is that the jet meters the amount of fuel passing to the engine. What really determines fuel mileage, howeverj is the amount of throttle opening necessary to obtain the required power with a correct mixture, if the engine is not developing pow or efficiently a wider throttle opening will be needed at all times, and luel consumption will be raised, irrespective ol : jet size. A very small jet, in fact, may increase fuel consumption by making necessary constant use of lower gears. If a, certain jet size once gave economical running, it is necessary to look boyond the carburettor for the reasons for - increased fuel consumption. Begin by checking compression with the starting handle, for faulty valves and rings allow total loss of gas which should be converted into power. The next point is ignition, for occasional misfiring means waste of a cylinder full of gas at a time. This fault u&ually develops with even the best of plugs after prolonged use, and the only way to guard against it is by installing a complete new set occasionaly. Tappet Adjustment. Many motorists regard accuracy in tappet adjustments as necessary merely in the interests of silence. Actually it has a profound effect on engine eificiency. A wide clearance not only reduces the period during which the valve is open, but reduces its lift as well. Both factors interfere with the "breathing'' of tlie cylinder. Too small a clearance soon causes expensive trouble in destruction of the valve by burning, and probable damage to the seating as well. The only way accurately to adjust tappets is by use of a feeler gauge, which can be bought very cheaply. The intervals at which engines need valve grinding vary enormously. The manner in which the car is driven and cared for is of considerable importance, but some engines are naturally hard on valves. Generally an engine with pump water circulation gives least trouble with valves. This is because it is possible to arrange the water passages so that the water is pumped faster round the exhaust valves, which are the hottest part of the engine. An Extravagance. Besides being extravagant in fuel, an engine which runs with the radiator at a very low temperature is rot necessarily well cooled, for the valves may still burn out rapidly. Whether tlio engine runs cold or at the normal temperature of 160-180deg. should make no difference to the valves, but it will affect fuel consumption and power very materially. Fit a thermometer, which costs only a trifle, and experiment with blanking off portion of the radiator, so that normal temperature will be maintained during the winter. Make the screen readily detachable, so that extra cooling may be obtained easily if required for mountaineering. Itemoval of the fan belt is sometimes recommended as an alternative to blanking off, but it is not so good. Direction of the wind, whether ahead or astern, then becomes too important a factor, causing over-cooling or boiling in many cases. It is a fact that a perfectly cold engine uses four times as much fuel as when it has reached , normal. It ;is therefore an economy yi fuel to warm up before dx-iving away, besides ensuring against damage from defective lubrication.